Brother DCP 8085DN, Service Manual

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When the new toner detection machanism detects that the toner cartridge is replaced with a
new one, the developing bias voltage is initialized at the same time.
The toner used for the machine has a property that print density is light first and gradually
darker in the course of usage. The developing bias controls the toner property so that the
print density is constant from first to last.
To obtain a print result of a constant density all the time, the machine counts the number of
print pages immediately after the toner cartridge is replaced and changes the bias voltage
according to the accumulated number of prints with the toner cartridge.
The bias voltage is changed with the steps described below:
(1) When the new toner sensor detects that the toner cartridge is replaced with a new (full)
one, the developing bias is set to 400V (initialized).
(2) After that, the bias voltage is stepped down according to the number of prints. Ultimately,
the bias voltage is approximately 300V.
<When a new toner cartridge is inserted after "Replace Toner" is displayed>
Corresponding counter, Setting value Operation
Counter of toner cartridge changes +1
Page counter for each toner cartridge Reset (0)
Coverage for each toner cartridge Reset (0)
Developing bias voltage Reset (Initial setting)
[Used toner amount]
[Density]
[Voltage]
[Used toner amount]
[Density]
[Voltage]
Bias voltage
Toner property Actual control
Print density
Bias voltage
Print density